The present invention relates to the use and preparation of a layered catalyst to selectively hydrogenate C8-C19 diolefins to C8-C19 monoolefins. C8-C19 monoolefins are valuable intermediates in the manufacture of alkylbenzene detergent precursors. The layered catalyst composition comprises an IUPAC Group 10 metal and an IUPAC Group 11 metal on a layered composition support. The support comprises an inner core of a refractory inorganic component, such as cordierite and an outer layer of a refractory inorganic component, such as gamma alumina.
Most detergents that are on the worldwide market today are made of linear alkylbenzene sulfonates (LABS). The linear alkylbenzenes sulfonates are preferred because they biodegrade more rapidly than the branched variety. LABS are manufactured from linear alkyl benzenes (LAB). The petrochemical industry produces LAB by catalytically dehydrogenating linear paraffins to linear olefins and then alkylating benzene with the linear olefins in the presence of a catalyst. This linear paraffin dehydrogenation step produces as its major product linear monoolefins. However, it is also well known that the catalytic dehydrogenation step of linear paraffins also produces an amount of linear diolefins. These diolefins do not alkylate benzene in the same way as the monoolefins and therefore do not produce the desired detergent precursors. Selective diolefin hydrogenation converts the diolefins to monoolefins, which can then be used to produce LAB. A detailed outline of LAB processes is provided in U.S. Pat. No. 5,276,231, the contents of which are herein incorporated in its entirety.
The current industrial practice for selectively hydrogenating diolefins or unsaturated hydrocarbon fractions is based on the use of sulfided nickel catalysts operating at moderately high temperatures of approximately 185° C. (365° F.). Sulfur loss from the catalyst to the product occurs and sulfur must be replenished to keep the catalyst active and operating optimally. Furthermore, once the sulfur is lost into the product, in some instances the sulfur must also be removed from the product and this adds another level of processing. U.S. Pat. No. 4,992,157 describes a selective hydrogenation catalyst comprising sulfided nickel and an IUPAC Group 10 metal on an alumina/clay support.
Other types of selective hydrogenation processes are also known, such as that described in JP54157507A. JP 54157507A describes the use of a palladium catalyst on an alumina support to selectively hydrogenate acetylene and methyl acetylene (alkynes) that are present in olefin fractions obtained in petrochemical processes. The catalyst described in JP54157507A comprises a thin alumina coating over an alpha alumina carrier of spherical or cylindrical shape and being around 1-20 mm in size, length and diameter. The alumina precursor, which can be aluminum nitrate, aluminum chloride, aluminum hydroxide and the like, is coated onto the alpha alumina carrier and then the coated alpha alumina carrier and alumina precursor is heat treated at between 400° C. (752° F.) to 700° C. (1292° F.) to create a thin alumina coating over the alpha alumina carrier. A palladium compound such as palladium chloride, palladium nitrate, and the like is dissolved in a suitable solvent, and then applied to the alumina coating to give effectively an enriched surface coating containing palladium. JP54157507A describes the use of the resulting catalyst in the selective hydrogenation of acetylene in a composition comprising ethylene.
The process disclosed herein has been developed to enable one to selectively hydrogenate C8-C19 diolefins to C8-C19 monoolefins at relatively high space velocities using a layered catalyst that eliminates the need to use a sulfided nickel catalyst for associated sulfur addition (and in some instances the subsequent removal of sulfur from the product).